The present invention relates to rotors for caliper disc brakes and the like, and in particular to an improved rotor with a cross vented hat section and method of making same.
Rotors are generally well known in the art, and are used extensively in vehicle braking systems, power transmission devices, clutches, and other similar machinery and mechanisms. Vehicle caliper disc braking systems slow the vehicle by inhibiting the rotation of the vehicle wheels. Rotors used in typical braking systems include a central hat section for attaching the rotor to a vehicle wheel and drive member for rotation therewith, and an annular peripheral section having friction surfaces disposed on opposite sides.
A caliper assembly secured to a non-rotating component of the vehicle, such as the vehicle frame. The caliper assembly includes a pair of brake pads disposed adjacent the rotor friction surfaces, and a moveable piston operatively connected to one or more of the brake pads. When the driver brakes the vehicle, hydraulic or pneumatic forces move the piston which clamps the pads against the friction surfaces of the rotating rotor. As the brake pads press against the moving rotor friction surfaces, frictional forces are created which oppose the rotation of the wheels and slow the vehicle. The friction converts the vehicle's kinetic energy into large quantities of heat, much of which is absorbed by the friction surfaces and conducted to the rest of the rotor and to other components to which the rotor is connected.
Excess heat leads to premature brake wear and/or failure. Therefore a brake rotor should quickly transfer and dissipate the heat generated during braking. Vents have been formed in the friction surface of the rotor to circulate air around the friction surface for cooling the brake. However, the circulated air does not effectively reach other portions of the rotor such as the hat section and these portions continue to retain the unwanted heat. The hat section also blocks the circulated cooling air from the other vehicle components such as the spindle or axle which are heated during braking. It is desirable to cool the hat section of the rotor and the vehicle components to which the rotor is mounted.
Brake rotors are typically cast from a ferrous material such as cast grey iron, and then are machined in multiple operations to shape the hat section and friction surfaces. In general, solid cast iron or cast aluminum rotors are preferred from the standpoint of strength. Rotors having vented friction surfaces, however, are typically produced by initially casting a solid rotor which is then subjected to relatively extensive machining operations to form the vents. While this has proven to be an effective means of producing vented rotors, the additional machining operations increase the cost of manufacturing such rotors. It would therefore be advantageous to provide a method of forming a rotor having a vented hat section which is less expensive than the conventional method of forming vents, and which may not be significantly more expensive than the conventional method of forming a full cast, solid rotor.